Quarter	Percent
1998-01-01	40.5
1998-04-01	40
1998-07-01	39.6
1998-10-01	39.7
1999-01-01	38.2
1999-04-01	38.2
1999-07-01	38.7
1999-10-01	38.9
2000-01-01	38.4
2000-04-01	37.8
2000-07-01	37.6
2000-10-01	38.1
2001-01-01	37.6
2001-04-01	38.2
2001-07-01	38.4
2001-10-01	38.8
2002-01-01	37.8
2002-04-01	36.4
2002-07-01	35.9
2002-10-01	35.6
2003-01-01	35.4
2003-04-01	34.7
2003-07-01	34.2
2003-10-01	34.1
2004-01-01	32.8
2004-04-01	32.4
2004-07-01	31.9
2004-10-01	32.1
2005-01-01	32.1
2005-04-01	31.5
2005-07-01	31.5
2005-10-01	31.3
2006-01-01	31.4
2006-04-01	30.8
2006-07-01	30.2
2006-10-01	30.7
2007-01-01	30.9
2007-04-01	30.5
2007-07-01	30.7
2007-10-01	31.2
2008-01-01	30.9
2008-04-01	30.5
2008-07-01	30.2
2008-10-01	30.2
2009-01-01	29.5
2009-04-01	28.8
2009-07-01	28.6
2009-10-01	28.5
2010-01-01	28.2
2010-04-01	27.4
2010-07-01	27.4
2010-10-01	27.6
2011-01-01	27.4
2011-04-01	27.8
2011-07-01	27.2
2011-10-01	26.4
2012-01-01	26.3
2012-04-01	26.1
2012-07-01	25.9
2012-10-01	25.8
2013-01-01	26.2
2013-04-01	25.3
2013-07-01	25.3
2013-10-01	26
2014-01-01	25.2
2014-04-01	24.5
2014-07-01	24
2014-10-01	23.9
2015-01-01	23.3
2015-04-01	22.1
2015-07-01	21.8
2015-10-01	22.1
2016-01-01	22.0
2016-04-01	21.9
2016-07-01	21.9
2016-10-01	23.2
2017-01-01	23.4
2017-04-01	22.1
2017-07-01	22.8
2017-10-01	23.7
2018-01-01	24.0
2018-04-01	22.8